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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46486 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kkBrh-0001tP-Sv for qemu-devel@archiver.kernel.org; Tue, 01 Dec 2020 15:03:09 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:52172) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kkBqU-00013e-3d for qemu-devel@nongnu.org; Tue, 01 Dec 2020 15:01:54 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:43413) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kkBqP-0001KQ-R3 for qemu-devel@nongnu.org; Tue, 01 Dec 2020 15:01:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606852908; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=p08iSY+kgBnjqJyreM/eyA6iPuemeoYxK+gGxA5dnnM=; b=IoyH2P7MZ11g2Ttl9d8fhppHZXHRctS9GGRXMOIIRipRZhcS2HV8m1IPfKA7S6nSUB+1pF pgykKd47RxoEJQ3EEd6RJxNc0jbUjri5irYLJJQ78injcm8senuBrrOiLibhqmRUyRMM6n GX0W6FBQqvBtH/W+rrrpHC5JU5zXOpU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-414-Pl55aTfwMOa8ETXcJcqUWw-1; Tue, 01 Dec 2020 15:01:46 -0500 X-MC-Unique: Pl55aTfwMOa8ETXcJcqUWw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3754C858182; Tue, 1 Dec 2020 20:01:45 +0000 (UTC) Received: from work-vm (ovpn-115-1.ams2.redhat.com [10.36.115.1]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 634F560BFA; Tue, 1 Dec 2020 20:01:40 +0000 (UTC) Date: Tue, 1 Dec 2020 20:01:37 +0000 From: "Dr. David Alan Gilbert" To: Peter Xu Subject: Re: [PATCH v4 0/6] UFFD write-tracking migration/snapshots Message-ID: <20201201200137.GQ4338@work-vm> References: <20201126151734.743849-1-andrey.gruzdev@virtuozzo.com> <20201201070820.GO105758@angien.pipo.sk> <20201201105300.GQ105758@angien.pipo.sk> <20201201184055.GM4338@work-vm> <20201201192247.GF3277@xz-x1> MIME-Version: 1.0 In-Reply-To: <20201201192247.GF3277@xz-x1> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.497, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Krempa , Juan Quintela , qemu-devel@nongnu.org, Markus Armbruster , Paolo Bonzini , Den Lunev , Andrey Gruzdev Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Xu (peterx@redhat.com) wrote: > On Tue, Dec 01, 2020 at 06:40:55PM +0000, Dr. David Alan Gilbert wrote: > > > Yep, seems that current userfaultfd supports hugetlbfs and shared memory for > > > missing pages but not for wr-protected.. > > > > For hugepages, you'd need kernel support - but also you'd want to make > > sure you write the whole hugepage at once. > > Or we can do similar things by splitting the huge pages just like when we > migrate. > > I should have overlooked these facts when I replied previusly - we do need the > same logic, but also special care on these special memory types. > > > > > For shared, there's a harder problem to ask; what happens if RAM is > > written by the other process - for postcopy, we get the other process > > to send us a userfaultfd that they have registered with their VM. > > Good point... so we should need similar things too. > > Looks like we'd better explicitly disable shmem/hugetlbfs for now from qemu > background snapshots before we have prepared these utilities, just in case it > got run on some "future" kernels and accidentally got enabled, so the snapshot > files could be corrupted ones. > > Is shmem used a lot in libvirt, or is it even a default configuration? No, but it's used with vhost-user applications; like dpdk. Dave > -- > Peter Xu > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK